tsan: add support for linux/powerpc64 in buildgo.sh

The current implementation of the Go sanitizer only works on x86_64.
Added some modifications to the buildgo.sh script and the Tsan code
to make it work on powerpc64/linux.

Author: cseo (Carlos Eduardo Seo)
Reviewed in: https://reviews.llvm.org/D43025

llvm-svn: 330122